1. Field of the Invention
The present invention relates to a camera, and more particularly to a camera for an IX240 type photo film cartridge, that has a door driving mechanism for operating a door member of the cartridge in cooperation with a cover that slides between a cartridge exchange position for permitting loading and unloading the photo film cartridge, a work position for permitting photography, and a rest position for deactivating the camera.
2. Background Arts
The IX240 type photo film cartridge contains the whole length of a photo filmstrip inside its cartridge shell, and advances the photo filmstrip out of the cartridge shell when a spool of the cartridge is rotated in an unwinding or advancing direction. While the whole length of the photo filmstrip is contained in the cartridge shell, a film port is closed by a light-shielding door member that swings inside the film port to open and close the film port. A spool locking mechanism is interconnected with the door member, to lock the spool when the door member is closed. The spool is unlocked by opening the door member.
The IX240 type camera is provided with a door driving mechanism for opening and closing the door member of the photo film cartridge as loaded therein. The door driving mechanism opens the door member after the photo film cartridge is inserted in a cartridge chamber and is closed light-tightly. After the entire length of the photo filmstrip is rewound into the cartridge shell, the door driving mechanism closes the door member.
One type of the door driving mechanism is driven by a motor or an actuator to open and close the door member, and another type is manually operated for the sake of power-saving and compactness. Japanese Laid-open Patent Application No. 10-104712 (U.S. Pat. No. 5,943,520) discloses a compact camera with a sliding cover that slides on a camera body between a rest position covering most of the camera body and a work position uncovering photographic elements of the camera which are necessary for photography. This camera has a door driving mechanism that opens and closes the door member of the IX240 type photo film cartridge in cooperation with the sliding cover.
The sliding cover is overlaid on the lid of the cartridge chamber in the work position as well as in the rest position, so as to prevent opening the lid. To open the cartridge chamber lid, the sliding cover must be slid further in the uncovering direction from the work position to a cartridge exchange position. In order to prevent the sliding cover from sliding unexpectedly to the cartridge exchange position, a safety lock mechanism is provided for locking the sliding cover at an intermediate position between the work position and the cartridge exchange position.
When the sliding cover is moved back to the work position or the rest position after a new photo film cartridge is loaded in the IX240 type camera, the camera automatically detects condition of usage of the photo film cartridge and also reads film data of the filmstrip, such as film speed and film type, from a data disc that is mounted on the spool of the photo film cartridge. So the spool is rotated by a motor in a rewinding direction for reading the film data. Therefore, if the door member is not fully opened and thus the spool is not completely unlocked at the work position or the rest position of the sliding cover, the spool locking mechanism would be broken when a rotational power is applied from the motor to the spool. On the other hand, if the door member is not completely closed when the sliding cover reaches the cartridge exchange position and the cartridge chamber lid is open, the photo filmstrip would be fogged. For these reasons, the door driving mechanism is required to finish opening the door member of the newly loaded photo film cartridge before the sliding cover is moved back to the work position, and finish closing the door member before the sliding cover reaches the cartridge exchange position.
However, the door driving mechanism disclosed in the above prior art finishes opening or closing the door member just when the sliding cover reaches the work position or the cartridge exchange position respectively. Therefore, there remains some possibility of breaking the spool lock mechanism or fogging the photo filmstrip.
Moreover, since the door member swings to open and close the film port, the door driving mechanism must convert the sliding movement of the sliding cover into a rotational movement for actuating the door member. For this reason, the door driving mechanism has been complicated, so it has been difficult to slide the cover smoothly when it is connected with such door driving mechanism.
In view of the foregoing, an object of the present invention is to provide a camera with a sliding cover that ensures the door member to be opened or closed completely in response to a small movement of the sliding cover that can be slid by a small force.
A camera according to the invention comprises:
a camera body directed to loading a photo film cartridge having a light-shielding door member mounted pivotally in a film port thereof to rotate between a closed position and an open position for closing and opening the film port respectively;
a cover member mounted on the camera body and movable between a cartridge exchange position for permitting loading and unloading the photo film cartridge, a rest position for deactivating the camera, and a work position for permitting photography through the camera, the cover member prohibiting loading or unloading the photo film cartridge in the rest and work positions;
a door drive shaft that is engaged with one axial end of the door member when the photo film cartridge is loaded, for rotating the door member between the closed position and the open position;
an input member that rotates together with the drive shaft;
an urging member for urging the drive shaft to rotate alternatively in a direction to open the door member or in a direction to close the door, such that the urging member urges the drive shaft in the opening direction and holds the door member in the open position after the drive shaft rotates through a predetermined angle in the opening direction from the closed position of the door member, whereas the urging member urges the drive shaft in the closing direction and holds the door member in the closed position after the drive shaft rotates through a predetermined angle in the closing direction from the open position of the door member; and
an engaging member that engages the cover member with the input member only while the cover member moves between the work position and the cartridge exchange position, for causing the input member to rotate in the closing direction as the cover member moves from the work position to the cartridge exchange position, and causing the input member to rotate in the opening direction as the cover member moves from the cartridge exchange position to the work position.
Because the cover member is engaged with the input member only while the door member is moved between the work position and the cartridge exchange position, the door member is not rotated while the cover member is moved between the work position and the rest position. So the photo filmstrip would not be pinched by the door member during the usual operating condition of the camera. Because of the urging member, the door member is completely closed and held in the closed position before the cover member reaches the cartridge exchange position, or completely opened and held in the open position before the cover member reaches the work position. Accordingly, the photo filmstrip would not be fogged on unloading the photo film cartridge, or the spool of the photo film cartridge is unlocked and is enabled to rotate without any hindrance as soon as the cover member reaches the work position.
According to a preferred embodiment, the input member is a pinion that rotates in coaxial with the drive shaft, and the engaging member comprises a rack provided securely on the cover member. The cover member preferably slides on the camera body between the cartridge exchange position and the work position and the rest position. According to this configuration, linear movement of the cover member is converted into rotational movement through a simple mechanism with a high reliability without lowering smoothness of the movement of the cover member. Thus, the present invention provide a simple and stable door driving mechanism with a low cost.